Thread by @The_Corres

THREAD🌿🦑🌾🦟

Along with the #ClimateCrisis, biodiversity loss is the most pressing problem we face today. But it’s hard to understand what this even means.

So here’s a crash-course by @tamarstelling!

This is what the Earth’s living layer actually consists of 1/:

Last May, the @IPBES – like, the United Nations for biodiversity and ecosystems – stated: " a million species are threatened with extinction".

Crap! 💩 But… what is a species? How many do we have and how many have we lost? And how did we not notice this happening?! 2/

We don’t know how many species exist for three reasons:

1. We haven’t discovered all life on earth yet

2. We may accidentally have *rediscovered* some species. Several times (... oops)

3. Biologists disagree about what a species actually *is*

3/

(Yes, there are *over 20* definitions, you can nerd out over them all here: scientificamerican.com/article/what-i…)

BUT, these are the most recent estimates of species on land and sea 4/:

SO. We have all these species, and we know loads of species have already gone extinct, and now we’re told that another 1 million species are threatened.

How is this happening under our noses and we’re not noticing it?!

5/

Because nobody remembers how abundant nature was before their time. For us, it seems like only “rare” species go extinct, so we don’t notice it, because we can't remember them not being rare.

But, before a species goes extinct, it becomes rare where it was once abundant.

6/

For species that are already extinct, it’s definitely too late. But before a species is threatened with extinction, the greatest damage has already been done. How do we express this aspect of biodiversity?

(Here's a whale for fun. The images in the piece are by Leon de Korte) 7/

The answer: in biomass.

Prof Ron Milo + @yinonbaron of @WeizmannScience came up with Gross Biomass Product – kgs of living matter. How many kgs of creature are there today and how were there before?

When you look at biodiversity loss in this way, it becomes much more real. 8/

Looking at the species distribution on Earth, insects seem the dominant life form.

But we don’t live on Planet Insect.

Because viewed in terms of biomass, plants that have undisputed dominion. In fact, the presence of plants pretty much dwarfs all other forms of life.

9/

The way that biomass is calculated is, dare I say it, too complicated for Twitter.

Just read about it, here: thecorrespondent.com/336/climate-ch…

10/

But the main takeaway is this:

We currently have 500 gigatonnes of biomass. Before humans began rearing livestock, took up agriculture, and started the industrial revolution, there was an estimated 1,000 gigatonnes of carbon trapped in living matter.

11/

So in the last 1,000 years, we’ve destroyed *half* (!) of the Earth’s living layer!

It’s not about the extinction of this species, or that one, but about the overall plummeting biomass. And yes, it's plummeting.

12/

With this in mind, it becomes clear that the important question is not:

"How many species are about to disappear?"

Instead, it’s:

"At what rate exactly, are we eating away at the Earth’s living outer shell?"

13/

This question is just a starting point for follow-up Q’s like: are the systems that produce our food in balance with the natural environment?

Or: which species, classes or kingdoms are experiencing a strong biomass decline due to our need for X, Y and Z?

14/

If there’s one thing we do know, it’s that we can’t live on a dead planet.

But if we could, would we even want to?

And, does picturing biodiversity and its loss in terms of biomass help you understand: we’re destroying the Earth’s living layer? 15/
thecorrespondent.com/336/climate-ch…

If it doesn't help you understand – then what would?

Join Non-human Life correspondent @tamarstelling, Prof Ron Milo and @yinonbaron of @WeizmannScience, and Prof Mike Benton of @BristolBioSci to discuss this question under the article! END
thecorrespondent.com/336/climate-ch…

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